評論
打印
Recording One
錄音一
Governments, private groups and individuals spend billions of dollars a year trying to root out non-native organisms that are considered dangerous to ecosystems, and to prevent the introduction of new intruders.
政府、私人團體以及個人每年都花費了大量的金錢來清除那些被認為會危害當地生態系統的外來生物，以及預防新入侵者的引入。
But a number of scientists question the assumption that the presence of alien species can never be acceptable in a natural ecosystem.
這一觀點卻受到了很多科學家的質疑，他們對這些外來物種永遠也不會融入當地自然生態系統這一看法持懷疑態度。
They say that portraying introduced species as inherently bad is an unscientific approach.
他們說把外來物種描述成有害的是不科學的。
"Distinctions between exotic and native species are artificial," said Dr. Michael Rosenzweig, a professor of evolutionary biology at the University of Arizona,
亞利桑那大學進化生物學教授邁克爾·羅森茨維格博士說，外來物種和本地物種的區分是人為的。
"because they depend on picking a date and calling the plants and animals that show up after that date 'exotic.'"
“因為他們依賴于選擇一個日期，把這一天結束后出現的植物和動物稱為‘外來物種’”
Ecosystems free of species defined as exotic are, by default, considered the most natural.
默認情況下，沒有外來物種的生態系統被認為是最自然的生態系統。
"You can't roll back the clock and remove all exotics or fix habitats," Dr. Rosenzweig said.
羅森·茨威格博士說：“你不能讓時間倒流，消除所有外來物種，或者修復棲息地。”
"Both native and exotic species can become invasive,
“本土和外來物種都可能成為入侵物種，
and so they all have to be monitored and controlled when they begin to get out of hand."
因此，當它們開始失控時，所有物種都必須受到監視和控制。”
At its core, the debate is about how to manage the world's remaining natural ecosystems and about how, and how much, to restore other habitats.
這場辯論的核心是如何管理世界上現存的自然生態系統，如何以及多大程度上恢復其它棲息地。
Species that invade a territory can harm ecosystems, agriculture, and human health.
入侵物種可能會損害生態系統、農業和人類健康。
They can threaten some native species or even destroy and replace others.
它們可以威脅到一些本土物種，甚至摧毀和取代其它物種。
Next to habitat loss, these invasive species represent the greatest threat to biodiversity worldwide, many ecologists say.
許多生態學家表示，物種入侵僅次于棲息地的喪失，是全世界生物多樣性的最大威脅。
Ecologists generally define an alien species as one that people, accidentally or deliberately, carried to its new location.
生態學家通常將外來物種定義為人們偶然或故意帶到新地點的物種。
Across the American continents, exotic species are those introduced after the first European contact.
美洲大陸上的外來物種是在第一次接觸歐洲后引進的。
That date, rounded off to 1500 AD, represents what ecologists consider to have been a major shift in the spread of species, including crops and livestock,
那一天，約在公元1500年，標志著生態學家所認為的物種（包括農作物和牲畜）傳播的重大轉變。
as they began to migrate with humans from continent to continent.
當他們開始和人類一起從一個大陸遷移到另一個大陸的時候。
"Only a small percentage of alien species cause problems in their new habitats,"said Don Smith, professor of ecology and evolutionary biology at the University of Tennessee.
“只有一小部分外來物種給新棲息地帶來麻煩，”田納西大學生態學和進化生物學教授唐·史密斯說。
"Of the 7,000 alien species in the United States-out of a total of 150,000 species-only about 10 percent are invasive," he pointed out.
他指出：“美國物種達15萬，7000是外來物種，只有10%屬于入侵物種。
The other 90 percent have fit into their environments and are considered naturalized.
另外的90%已經適應了環境，被歸化了。
Yet appearances can deceive, ecologists caution,
然而，生態學家警告說，這些表象可能并不是真的，
and many of these exotics may be considered acceptable only because no one has documented their harmful effects.
而且，這些外來物種中有許多可能被認為是可接受的，只是因為沒有人記載過它們的有害影響。
What is more, non-native species can appear harmless for decades, then turn invasive.
更重要的是，幾十年內非本地物種可能會看起來無害，然后變得具有侵略性。
Questions 16 to 18 are based on the recording you have just heard.
根據你剛才聽到的錄音回答16-18題。
16. What assumption about introduced species is challenged by a number of scientists?
問題16：許多科學家對引進物種的假設提出了質疑。
17. What does Dr. Michael Rosenzwei think of exotic and native species?
問題17：邁克爾·羅森茨維格博士對外來和本地物種有何看法?
18. What does Professor Don Smith say about alien species?
問題18：關于外星物種，唐·史密斯教授說了些什么?
